Effects of increased physical activity and mild calorie restriction on heart rate variability in obese women

The effects of exercise and mild caloric restriction on heart rate variabil ity (HRV) were investigated in 12 mildly obese, normotensive Japanese women aged 45.8 +/-4.2 (SEM) years with a body mass index (BMI) of 27.3 +/-0.4 k g/m(2). The subjects participated in a 3-month program aimed at increasing physical activity and modifying eating behavior (intervention group). The c ontrol group consisted of 12 women (age 50.1 +/-4.8 years. BMI 27.2 +/-0.6 kg/m(2)) who did not attend the program. The frequency domain of HRV was ca lculated from 5-min Holler recordings while the subjects rested in a supine position. After 3 months, BMI decreased to 25.0 +/-0.5 kg/m(2) (p <0.001 v s baseline) in the intervention group. which was accompanied by decreases i n body fat mass, waist circumference, serum total cholesterol and triglycer ides, and improvement in insulin sensitivity. The mean and SD of the RR int ervals. total power, and low and high frequency power of HRV significantly increased after the intervention. whereas no significant changes were seen for the controls. The changes in these HRV variables (calculated by subtrac ting the baseline values from the follow-up values) negatively correlated w ith the change in waist circumference, with the Pearson correlation coeffic ients being between -0.50 and -0.62 (p <0.05). A negative correlation was a lso seen between the changes in high frequency power and insulin resistance estimated by homeostasis model assessment (r=-0.49. (p <0.05). The combina tion of exercise and mild calorie restriction led to changes in HRV indicat ive of an improvement in parasympathetic modulation.